One of the most feared of these feedback loops is the vast amount of organic material currently trapped in permafrost, which would release methane and other greenhouse gases in large amounts given the right conditions.

And now a team of researchers has discovered another significant source of emissions that would result from the thawing of the tundra. For the frozen ground acts as a cap on much more ancient gas deposits, preventing them from escaping into the atmosphere.

The new study, of 10,000 square kilometres of the Mackenzie Delta in Canada, found that the seeps there were responsible for 17 per cent of the total emissions from the land even though they were only found in about one per cent of the area, according to a paper in the journal Scientific Reports.